This invention relates to a device for protecting the coolant circulation of an internal combustion engine, such as a motor vehicle engine, from excess pressure. The device includes a pressure control valve arranged in the upper region of a coolant-conducting tank and adjusted to an opening pressure p.sub.1.
The pressure control valve of a coolant circulating system of the initially mentioned type is conventionally adjusted to an opening pressure of about 1.1 to 1.15 bar. When the pressure in the coolant-circulating system exceeds this value, coolant, gases or water vapor may be discharged through this pressure control valve. When an internal-combustion engine has been operated for a certain time and has thus been heated up and subsequently switched off, vapor may be created by local overheating, for example, at the cylinder heads. When the coolant circulation is interrupted, the forming vapor cannot escape. The volume of fluids in the tank will be increased by this vapor formation resulting in the danger that coolant will be ejected via the pressure control valve. The control valve will then be unavailable for normal operation. In order to reliably prevent the ejection of coolant in the switch-off phase of an internal combustion engine operation, it would be possible to protect the coolant circulation by means of a higher excess pressure, i.e., to adjust the pressure control valve to a higher opening pressure. However, in the normal operation, this would result in increased stress on the parts of the cooling system.
An object of the present invention is to provide a device of the initially mentioned type wherein the ejection of coolant after the switching-off of a heated-up internal combustion engine is prevented.
Another object of the present invention is to prevent coolant ejection without having to protect the whole coolant-circulation system during operation by means of an increased excess pressure.
These and other objects of the present invention are attained by the arrangement of a float in the tank which is assigned to an admission means of the pressure control valve in a sealing manner.
According to the present invention, in the case of a formation of vapor because of local overheating and the accompanying increase in volume, the coolant level rises in the tank and displaces the float. As a result, the float is positioned in a sealing manner upstream of the pressure control valve. Thus, there is no longer a direct connection between the interior of the coolant-holding tank and the pressure control valve and coolant cannot be ejected. By means of the increased excess pressure that is now accomodated by the coolant-circulation system, a further formation of vapor is now essentially prevented. Sometime after the switching-off of the internal combustion engine, the coolant level in the tank will fall again because of cooling. The float will then disengage itself from its seat upstream of the pressure control valve so that the cooling-water circulation will again be protected by means of the opening pressure p.sub.1 at which the pressure control valve is actuated.
In a further development of the invention, a second pressure control valve is provided which is designed for a higher opening pressure p.sub.2 than the first pressure control valve. The increased opening pressure of the second pressure control valve which, for example, is 1.5 bar, prevents an excessive pressure build-up in the coolant circulating system when vapor formation occurs during the switch-off phase of the internal combustion engine. The opening pressure p.sub.2 of the second pressure control valve is advantageously selected in such a way that, on the one hand, the danger of damage because of increased stress to the parts of the coolant-circulating system because of the high pressure is precluded. On the other hand, during this switch-off phase of the internal combustion engine, the formation of vapor is reduced and the ejection of coolant is prevented.
In an advantageous development of the invention, it is provided that the second pressure control valve is installed in the float and connects the admission means to the first pressure control valve with the tank. The second pressure control valve is thus connected in series with the first pressure control valve. Thus an addition of pressure is created between the opening pressures of both pressure control valves so that the second pressure control valve must be designed only with respect to the difference between the opening pressure of the first pressure control valve and the desired increased opening pressure. In the case of a formation of vapor during the switch-off phase of the internal combustion engine, i.e., when there is the danger of an ejection of coolant, the coolant circulation is thus protected via the added opening pressures.
In a further development of the invention, it is provided that the float is guided in a cage arranged in the tank. Thus it is ensured that the float always moves in a defined path. In a further development, it is provided that the float, with the second pressure control valve and with the cage, is designed as an insert that, in a sealing manner, can be inserted into an opening of the tank and contains the admission means to the first pressure control valve. This insert forms a structural unit that can be preassembled and inserted into the tank as a whole.
In a further development of the invention, it is provided tha the insert is inserted into a filler connection piece of the tank and has a valve seat for the valve disk of the first pressure control valve that is held by means of a bayonet-type cap. Thus a structural unit is formed from both pressure control valves which as such is mounted at the tank. The filler connection piece of the tank may then have a relatively simple design.
In a further development of the invention, it is provided that the insert has a tube-shaped projection connecting to the admission means to the first pressure control valve. A float is guided in said projection with play, and the end of said projection which points into the tank is subdivided into individual legs by means of axial slots. In this manner, a simple cage for the guiding of the float is obtained, on the one hand, while, on the other hand, the tank is protected from overfilling. As long as the float is located in the area of the slots of the projection, a relatively large opening cross-section to the tank is free, through which the coolant may enter the tank. When the float reaches the unslotted area of the projection, due to the rising liquid level, only a small free cross-section remains so that a further entry of coolant into the tank is at least considerably impaired.
In an advantageous development of the invention, it is provided that the legs of the projection, at their free ends, are equipped with stops that are radially aimed toward the inside of the projection. When the float is inserted, the legs are elastically spread apart slightly. After the insertion of the float, the legs secure the lowest position of the float. The float thus, in a simple manner, can be fitted together with the insert to form a structural unit.
In a further development of the invention, a throttle opening bypassing the float is provided from the interior of the tank in front of the first pressure control valve. Thus it is achieved that when the coolant-circulating system is overfilled, the pressure in the cooling-water circulating system can decrease over a predeterminable time period to the opening pressure of the first pressure control valve. Accordingly, even in the case of overfilling, the coolant-circulating system is not subjected to increased pressure over a longer period of time. The cross-section of the throttle opening is selected in such a way that during the switch-off phase of the engine no coolant ejection takes place in the case of a normal charge through the throttle opening. In the case of a first embodiment, the leading-in of the throttle opening is arranged in the area of the highest point of the tank. As a result, the excessive pressure is decreased by means of the discharge of gas or water vapor. In the case of another embodiment of the invention, it is provided that the leading-in of the throttle opening is arranged at a point that immerses in the cooling water. As a result, the pressure is decreased by the ejection of coolant, in which case, however, only that quantity of coolant is ejected that may be present because of a possible overfilling.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.